Field of the Invention
The present invention relates to a transfer molding method and a transfer molding device that mold a hollow molded article with a thermosetting resin, and to a molded article.
Description of the Related Art
Heretofore, as a method for molding a hollow component by an injection molding method, a method is known which molds a divided body by primary molding, and makes a plurality of divided bodies abut on and join with one another by secondary molding. For a molding device, a die sliding system is known for sliding a die between the primary molding and the secondary molding. Further, a system (Japanese Patent Laid-Open No. H11-042670 (1999)) is known in which a divided body is molded with an intermediate die sandwiched between a lower die and an upper die (primary molding) and, subsequently, the intermediate die is released to make the lower die and the upper die abut on each other so as to perform molding (secondary molding), and then the divided bodies on which the primary molding has been performed using the both dies are joined with each other.
Further, as for a molded article requiring high dimensional accuracy, since a large amount of filler having a small line expansion rate such as silica is included in a resin, flowability of the resin is deteriorated when it is injected. Therefore, when material including a large amount of filler is molded, a transfer molding method that can easily deal with the material having a low flowability is used.
Of the transfer molding method, as a method for obtaining multiple pieces of molded articles, a method (Japanese Patent Laid-Open No. S58-225642(1983)) is known in which a plurality of thin dies is layered, and molding is performed over a plurality of stages at a time using a multiple-stage passing-through chamber.
As described in Japanese Patent Laid-Open No. H11-042670(1999), in an injection molding method for injecting from a side face of the intermediate die into the upper die and the lower die, a T-shaped runner, for example, is formed inside the die. When the molding is performed using the thermosetting resin, since the resin left in the runner inside the intermediate die becomes hard along with the molding (hardening) of the divided body, post handling including breakdown cleaning may be necessary. Particularly, it is remarkable for the resin having quick hardening reaction. Further, even though the runner for the primary molding is disposed on an abutment face of each die to avoid the breakdown cleaning of the die, since the different runners between the primary molding and the secondary molding are used, the resin needs to be injected from a plurality of points, thereby making the device complicated. There is a problem in which the device becomes further complicated to mold a layered component of the divided bodies including three stages or four stages.
The transfer molding method according to Japanese Patent Laid-Open No. S58-225642(1983), the plurality of the divided bodies can be molded at a time using the die including a plurality of stages. As the method for joining the divided bodies with one another, a method is known for inserting the divided bodies into another device to perform the molding. However, with this method, there is a problem in which, since the divided bodies are released from the die once, positioning of the divided bodies to be joined with one another is difficult and, in addition, a dimensional accuracy is hard to be realized due to warpage of the divided bodies.